About 700 years ago, people started to make mechanical clocks.
At first, they used wights to power these clocks.
The clocks told the hour with bells.
However, the wights were big and heavy, so these clocks were diffiicult to move.
About 500 years ago, people improved their clocks.
They used springs to power the clocks.
The springs were small and light.
So people could move the clocks easily.
Eventually, people began to carry watches.
Today, we have clocks and watches everywhere.
This is the result of many great inventions and many people's efforts.
Even now, clocks and watches are improving.
We can not really see time, but ancient people tries to recognize it.
They used different ideas and technologies to measure it.
When we look at our clocks and watches, we can easily see the time.
Now it is time to recognize the wisdom of those ancient peopl
